A conventional display device, such as a mobile phone or a display device equipped in a tablet, has relatively insufficient brightness due to strong external light when it is used outdoors, so that displayed images of ten have poor contrast, and users can not view the images very well. The existing solution is to equip more light sources of the backlight module or use a higher current to drive the backlight module. If more light sources are used, manufacture cost will increase, and more electrical power is also consumed. If a higher current is used to drive the light source, the service life of the light source is reduced, and it also consumes more electrical power.
The information disclosed in this “BACKGROUND OF THE INVENTION” section is only for enhancement understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art. Furthermore, the information disclosed in this “BACKGROUND OF THE INVENTION” section does not mean that one or more problems to be solved by one or more embodiments of the invention were acknowledged by a person of ordinary skill in the art.